code: def test_perimeter():
      for r in (40, 80, 160):
          disk = mh.disk(r, 2)
          p = mahotas.labeled.perimeter(disk)
          p_exact = r * np.pi * 2
          assert 0.9 < (p / p_exact) < 1.1
  
imports: import numpy
  import mahotas
  import mahotas.labeled
  from pytest import raises
label_desc: Use image node_id 19 for calling a global function with example usage: test_perimeter() without return types